1. Field of the Invention
The present invention relates to a light emitting device package and a method of manufacturing the same, and more particularly, to a light emitting device package wherein no Zener diode is mounted in the light emitting device package, and therefore, the light emitting device package can be used as a thin surface mount device (SMD), and a method of manufacturing the same.
2. Discussion of the Related Art
Generally, it is possible for a light emitting device, such as a light emitting diode or a laser diode, using Group III to IV or Group II to VI compound semiconductor materials of a direct transition compound semiconductor to emit various color light, including red color light, green color light, blue color light, and ultraviolet rays, with the development of a thin film growing technology and device materials. Also, it is possible for the light emitting device to emit white color light having high efficiency through the use of a fluorescent material or the combination of colors. With the progress of such a technology, the light emitting device has been increasingly applied to a transmission module of optical communication equipment, a light emitting diode backlight substituting a cold cathode fluorescent lamp (CCFL) constituting a backlight of a liquid crystal display (LCD), a white light emitting diode illuminating apparatus, a headlight for vehicles, and a signal light as well as a display device.
Hereinafter, the structure of a conventional light emitting device and a conventional light emitting device package will be described in brief with reference to the accompanying drawings.
FIG. 1 is a sectional view schematically illustrating the structure of a light emitting device mounted in a conventional light emitting device package. The structure of the conventional light emitting device will be described with reference to FIG. 1.
As shown in FIG. 1, the conventional light emitting diode includes a substrate 10, a buffer layer 11, an n-semiconductor layer 12, an active layer 13, a p-semiconductor layer 14, a transparent electrode 15, an n-electrode 16, and a p-electrode 17. Specifically, the buffer layer 11 and the n-semiconductor layer 12 are sequentially stacked on the substrate 10. At this time, a portion of the n-semiconductor layer 12 is etched to a predetermined depth, and the n-electrode 16 is formed on the etched portion of the n-semiconductor layer 12. The active layer 13, the p-semiconductor layer 14, and the transparent electrode 15 are sequentially stacked on the remaining portion of the n-semiconductor layer 12, which is not etched. The p-electrode 17 is formed on the transparent electrode 15.
When voltage from an external circuit is applied between the p-electrode 17 and the n-electrode 16 of the light emitting diode, holes and electrons are injected into the light emitting diode through the p-electrode 17 and the n-electrode 16, respectively. The holes and electrons are recoupled with each other in the active layer 13. As a result, residual energy is converted into light, which is discharged to the outside through the transparent electrode 15 and the substrate 10. The light emitting diode with the above-stated construction is mounted in a semiconductor device package, is changed into an electronic part through a predetermined process, and is then attached to a printed circuit board (PCB) together with other electronic parts. The semiconductor device package may be classified as an insertion type package or a surface mount type package.
The surface mount type package is highly integrated, is constructed in a thin form, and enables the embodiment of a system integration package as compared to the insertion type package. Consequently, a light emitting device package is mainly manufactured in the form of the surface mount type package.
FIG. 2 is a sectional view illustrating the structure of a conventional light emitting device package. The structure of the conventional light emitting device package will be described with reference to FIG. 2.
As shown in FIG. 2, a light emitting diode 30 and a Zener diode 40 are mounted on the upper surface of a first lead 21. The light emitting diode 30 is electrically connected to a second lead 22 and the Zener diode 40 via first bonding wires 52-1 and 52-2, respectively. The Zener diode 40 is electrically connected to the light emitting diode 30 and the first lead 21 via second bonding wires 54-1 and 54-2, respectively. The first lead 21, the second lead 22, the light emitting diode 30, and the Zener diode 40 are shielded by a molding part 60.
In the surface mount type light emitting device package with the above-stated construction, the light emitting diode is weak to static electricity or reverse voltage. For this reason, the light emitting device package further includes a bypass device for bypassing reverse current in order to complement the weakness of the light emitting diode. The Zener diode 40 is mainly used as the bypass device. As shown in FIG. 2, the Zener diode is electrically connected in parallel with the light emitting diode 30. Specifically, the Zener diode 40 is die-bonded using an adhesive resin, and then an n-electrode of the light emitting diode 30 and a p-electrode of the Zener diode 40 are connected in parallel with each other. Also, a p-electrode of the light emitting diode 30 and an n-electrode of the Zener diode 40 are connected in parallel with each other.
The Zener diode may be constructed in a pn junction structure (Zener breakdown occurs only in the reverse direction.) and a pnp (or npn) junction structure. In the pn junction structure, Zener breakdown occurs, and therefore, current is bypassed, only when the voltage is a reverse voltage. In the pnp (or npn) junction structure, on the other hand, Zener breakdown occurs, and therefore, current is bypassed, even when the voltage is a forward voltage as well as a reverse voltage. Consequently, the pnp (or npn) junction structure serves to safely protect the light emitting diode from abnormal current generated due to overvoltage or static electricity caused by external environment. The Zener diode having the pnp (or npn) junction structure is also called a back-to-back Zener diode. The electrodes of the Zener diode exhibit the same polarity, and therefore, the Zener diode has an advantage in that the Zener diode can be connected in parallel with the light emitting diode 30 irrespective of the polarities.
However, the conventional light emitting device package has the following problems.
The conventional surface mount type light emitting device package includes the metal leads. For this reason, there is needed an additional space necessary for mounting the protection device, such as the Zener diode. As a result, the total weight and size of the package are increased. Furthermore, a die bonding process for mounting the device and a wire bonding process for electrically connecting the device are individually carried out. Consequently, the process for manufacturing the light emitting device package is complicated and troublesome, and therefore, costs and time necessary for manufacturing the light emitting device package are increased.
In addition, it is difficult to manufacture the conventional light emitting device package through plastic injection molding, and therefore, the miniaturization and thin shaping of the light emitting device package are limited. Consequently, the conventional light emitting device package is not suitable for a current tendency requiring the reduction in weight and size of electronic products.